The invention relates to a stuffing box support assembly to be positioned between the production pumping tree and the stuffing box of a wellhead. The assembly provides means which enable the stuffing box to be tilted and/or shifted laterally relative to the axis of the pumping tree. As a result, the axis of the stuffing box can be aligned with the axis of the polished rod extending therethrough to reduce wear of the stuffing box packing.
The typical wellhead of a rod pumping well includes:
a tubing head, from which a string of production tubing is suspended;
a production pumping tree comprising a tubing head adapter connection, a production blowout preventer section, a flow tee section and a top connection;
a stuffing box; and
a pumping jack assembly for reciprocating the polished rod of a rod string which operates a downhole pump.
The stuffing box contains packing which seals around the polished rod to prevent fluid leakage.
The pumping tree and stuffing box together form a vertical joint bore extending therethrough.
The polished rod is sometimes axially or angularly misaligned relative to the axis of the pumping tree and stuffing box. As a result the polished rod bears against one side of the packing and wear and leakage soon occur.
It is known to provide a support assembly or adjustable joint between the pumping tree and the stuffing box to enable the axis of the latter to be tilted or shifted laterally to a limited extent. This is taught in U.S. Pat. No. 5,112,140, issued to Cherny et al. However the assembly shown in the ""140 patent stands quite tall.
It is the object of the present invention to provide a joint of this type which is compact and which is adapted to incorporate a flapper valve or like means to close off the joint bore in the event the polished rod parts or the rod string drops or is removed.
In accordance with a preferred and specific embodiment of the invention a support assembly is provided for connection between the upper end of a production pumping tree and the lower end of a stuffing box. The support assembly comprises:
A tubular lower housing forming a vertical bore having a reduced diameter lower bore portion, an expanded diameter intermediate bore portion and a further expanded diameter upper bore portion. The side wall of the housing forms a horizontal, annular, flat, internal shoulder at the junction of the intermediate and upper bore sections;
A lower ring, having a horizontal flat bottom surface and a spherically curved top surface, seated on the internal shoulder of the lower housing. The lower ring has a central opening of sufficient diameter to accommodate the polished rod with a lateral clearance. It also has a lateral clearance at its outer circumference with the side wall of the lower housing. The central opening of the lower ring is smaller than the diameter of the intermediate bore portion. As a result, the lower ring extends inwardly of the side wall of the lower housing. From the foregoing, it will be noted that the bottom ring can shift laterally, it enables the polished rod to extend therethrough and it permits the rod to shift or tilt within it. It also provides an overhanging support from which an underlying closure member, such as a spring activated flapper valve, may be suspended;
An upper housing having a tubular main body and a flange protruding outwardly from the bottom end of the main body. The flange has spherically curved top and bottom surfaces having a common center. The flange bottom surface is adapted to conform to the top surface of the lower ring and the flange is seated on the lower ring. The flange also has a lateral clearance with the side wall of the lower housing. The bore of the main body is sized to pass the polished rod with a lateral clearance. From the foregoing, it will be noted that the upper housing can tilt by sliding on the bottom ring and can shift laterally;
An upper ring, having a spherically curved bottom surface and horizontal flat top surface, seated on the flange top surface and conforming thereto. The upper ring extends around the main body with a lateral clearance and has a lateral clearance with the side wall of the lower housing. It will be noted that the upper ring permits the upper housing to tilt and it can move laterally with the upper housing;
An annular cap which threads onto the upper end of the lower housing side wall. The cap has a transverse wall which retains the upper ring, upper housing flange and lower ring in place on the annular shoulder, within the upper bore portion of the lower housing. The cap forms a central opening through which the main body of the upper housing extends with a lateral clearance;
Annular means, seated in the upper end of the main body bore, for centralizing the polished rod within the main body;
Means for sealing the assembly of rings and flange with the lower housing, to prevent leakage of pressurized fluid through the lower housing bore;
Means for sealing the centralizing means with the upper housing to prevent leakage of fluid therebetween; and
Closure means, such as a spring-actuated flapper valve, suspended from the lower ring, for automatically closing the lower ring opening when the polished rod is not present therein.
By means of this combination of components, the upper housing and its attached stuffing box may tilt with, move laterally with and remain coaxial with the polished rod.
Broadly, the invention involves:
the provision of a flange, on the upper housing, which has spherically curved top and bottom surfaces having a common center;
the provision of spherically curved bearing surfaces on the lower and upper rings, which conform to and bracket the flange, whereby the upper housing can tilt by sliding between them; and
the provision of the lower ring extending partway over the lower portion of the lower housing bore, to provide a support from which to suspend a bore closure means.
In one embodiment, the invention comprises a support assembly, for connection between the upper end of a production pumping tree and the lower end of a stuffing box and through which a polished rod will extend, comprising: a tubular lower housing having a side wall and upper and lower ends, the side wall forming a central bore therethrough, the bore having a lower portion and an expanded diameter upper portion, the side wall forming an annular flat internal shoulder at the junction of the upper and lower bore portions; a lower ring, having a flat bottom surface and a spherically curved top surface, seated on the shoulder, the lower ring having a central opening of sufficient diameter to accommodate the polished rod with a lateral clearance, the lower ring having a lateral clearance with the side wall of the lower housing; an upper housing comprising a tubular main body having upper and lower ends, the body lower end having an outwardly protruding flange, the flange being positioned in the upper portion of the lower housing bore and being seated on the lower ring, the flange having spherically curved upper and lower surfaces having a common center, the flange lower surface conforming to the top surface of the lower ring, the main body having a central bore extending therethrough for accommodating the polished rod, the flange having a lateral clearance with the lower housing side wall; an upper ring having a spherically curved bottom surface for conforming with and contacting the flange upper surface to retain the flange against upward movement; an annular cap attached to the upper end of the lower housing, the cap having a transverse wall having a bottom surface retaining the rings and flange within the expanded diameter upper portion of the lower housing bore, the cap wall forming a central opening through which the main body of the upper housing extends with a lateral clearance; and means, seated in the upper end of the main body bore, for centralizing the polished rod within the main body; whereby the upper housing may tilt coaxially with the polished rod and move laterally to a limited extent.